Place something over the pot to insulate it. Leaves work great but, a burlap sac would work.
You've probably already had your first frost so, it's to late to play with the soil but, after the spring thaw add some mulched leaves and/or cocoa bean hulls to the soil along with some manure, coffee ground, and/or some other greens.
Also, if you can find it purchase some rock phosphate and add that to the soil. If someone tells you to use you regular NPK salts (aka fertilizer) ignore them and don't use these products.
Yes, they provide your plant with Nitrogen, Phosphorous, and Potassium but, they break down soil structure, give the plants these nutrients in one blast and do not allow the plant the ability to regulate what nutrients it requires, these chemical fertilizer also kill beneficial soil biota.
Feed the soil, not the plants.